I. Field of the Invention
The present invention relates to a method and apparatus for attenuating noise resulting from fuel pump pulsation in a direct injection internal combustion engine.
II. Description of Related Art
Direct injection internal combustion engines have enjoyed increased acceptance for a variety of reasons. In particular, direct fuel injection into the engine combustion chamber typically results in better fuel economy and more efficient operation of the internal combustion engine.
In a direct injection internal combustion engine, a passageway is formed in the engine block, which includes the engine cylinder head, that is open to each combustion chamber. A direct injection fuel injector is then positioned within this passageway for each of the engine combustion chambers so that an outlet from the fuel injector is open to its associated combustion chamber.
Each fuel injector also includes an inlet that is connected by a fuel rail and typically a fuel pipe to a fuel pump. The fuel pump creates high pressure in the fuel rail and this high pressure, in turn, is fluidly connected to each fuel injector. Thus, upon activation or opening of each fuel injector, the injector injects the fuel directly into the engine combustion chamber.
One disadvantage of these previously known direct fuel injection engines, however, is that the fuel pump is typically cam driven and thus creates fuel pressure pulsations to the fuel rail. These fuel pressure pulsations, furthermore, vary in frequency in dependence upon the engine rpm. These fuel pump pulsations disadvantageously result in vibrations that are transmitted by the fuel injectors to the engine block and create an audible and undesirable noise as well as vibration and possible part fatigue.